The importance of E2A proteins as potent regulators of B- and T- cell formation is firmly established, but their role in activated B- or plasma cells remains unclear. We have recently amplified the cDNA encoding a B-cell restricted basic helix-loop-helix transcription factor member, designated activated B-cell factor 1, from a cDNA library prepared from human plasma cells. The expression pattern of ABF-1 has been demonstrated to be restricted to activated B-cells and EBV-transformed B cell lines. The proposed studies are aimed at investigating the cell- restricted regulatory elements that govern human ABF-1 gene expression as well as analyzing the genomic organization of ABF- 1. A broad spectrum of genetic and biochemical techniques will be used, including gene cloning and sequencing, DNA transfections, electrophoretic-mobility shift assays, Western- and Southern blotting and fluorescence microscopy. The results of these studies will identify transcription factors that regulate ABF-1 gene expression in activated B lymphocytes and EBV-infected B cells. In addition, they will provide important structural information regarding ABF-1 as well as map the chromosomal location of the ABF-1 gene.